The present invention relates to an improved structure for supporting and sealing a tubing string or a portion of a tubing string in a well and electrically insulating the tubing string or the portion of the tubing string from the remainder of the support structure or the tubing string.
In the production of oil and gas from wells, paraffin problems often appear. In treating such problems so that the paraffin does not build up sufficiently to create a restriction to the production the heating of the production string has commonly been attempted.
The I. C. Looman U.S. Pat. No. 2,244,256 discloses the removal of congealed paraffin and asphaltic bodies in oil wells and suggest the electrical heating of the wells. In this structure the tubing string hanger is insulated from the housing in which it lands by an annulus 19 of electrically insulating material preventing electric contact between the hanger and the housing. Additionally spaced insulators are mounted on the exterior of the tubing string and function as an insulating centralizer.
The L. H. Rhoads U.S. Pat. No. 2,597,261 discloses another similar structure in which an insulating bushing is provided between the cap at the upper end of the casing and the pipe line with additional insulating collars on the pipe line within the casing. This allows the use of an electric current passing through the pipe line to heat the paraffinic and sulphatic substances to maintain them in a free-flowing condition.
The C. A. Carpenter U.S. Pat. No. 2,728,396, the W. G. Green U.S. Pat. No. 2,982,354, the J. P. Brusco U.S. Pat. No. 2,812,818, the T. C. Dauphine U.S. Pat. No. 4,487,257 and B. J. Eastlund et al U.S. Pat. No. 4,716,960 all disclose similar insulating structures for the use of an electric current to maintain the well fluids in a free-flowing condition to allow maximum production.
The D. W. Blancher U.S. Pat. No. 2,667,626 discloses a telemetering system in which an insulating sleeve is used to provide the electrical insulation.
The E. T. Cugini U.S. Pat. No. 4,154,302 discloses an electric cable feed-through structure and the M. G. Zavertnik U.S. Pat. No. 2,896,972 discloses an insulating structure for insulating the tubular support of a hanging light fixture from the electric splice box.